It's not the urine or the smell, it's the feces that can be problems. But it is hard to get an illness from them (the disease is called toxoplasmosis). The poops have to be more than three days old, and you have to touch them and then put your fingers in your mouth and swallow the toxoplasmosis, and also the cat actually has to have toxoplasmosis at the time. In other words, there is not a lot to worry about. Cats don't go around with toxoplasmosis; if they do ever get it (some never do) they get over it. You're more likely to get toxoplasmosis if you garden without wearing gardening gloves (it's a soilborne microorganism) or if you eat rare meat.
Yeah just stay away from it and when someone changes it don't be in the same room so nothing gets stirred up in the air around you.
It's a chance if you touch it. If you don't change it, you'll be fine.